1. Field of the Invention
The present invention relates in general to digital audio broadcasting, and more specifically, to a method for performing a fast tune for a digital broadcast station in a radio receiver.
2. Description of the Related Art
With the introduction of terrestrial digital audio broadcasting, a radio listener has the opportunity to experience a higher quality of broadcast reception utilizing a digital broadcast as opposed to a traditional analog broadcast. Improved reception, better audio quality, and data services are some of the benefits of using digital audio broadcasting.
To receive the full benefits of digital audio broadcasting, listeners must have a digital audio receiver to receive the digital audio broadcast. Therefore, there will be a transition period as listeners migrate from analog audio receivers to digital audio receivers. During the transition period, if a broadcast station wants to maintain their listening audience, the broadcast station must transmit both a digital broadcast for those listeners who are capable of receiving the digital broadcast and transmit an analog broadcast for those listeners who are still utilizing the analog audio receiver.
A method of broadcasting both the digital signal and the analog signal a frequency range for a particular audio broadcast station has recently become available. In-Band On Channel (IBOC) is a system that is capable transmitting a hybrid signal. IBOC transmits the analog signal on a center portion of the frequency range with the digital signal occupying an upper and lower side portion of the frequency range.
An advantage with digital audio broadcasting is that the digital signal contains auxiliary program data, station identification information, or other information in addition to digital audio. The station identification information and auxiliary program data is useful in informing the listener as to the content of the broadcast signal without the listener having to wait to listen to a received broadcast to determine the contents thereafter. The digital signal contains, in part, a plurality of subcarriers each containing digital information representative of program data transmitted by the IBOC station. Information such as station identification (e.g., call letters), song title, artist, genre, and album are some of the information that can be quickly referenced by the listener. However, decoding and outputting the digital signal to the listener may be more timely than decoding and outputting an analog signal due to the complex decoding that is performed on audio and data subcarriers of the digital signal.
A lookup table stored in the receiver may be used to quickly obtain information on a broadcast station without having first received the audio broadcast signal from the broadcast station. The lookup table would contain station related information regarding a specific broadcast station such as station identification, genre, broadcast type, station location, station alias name, program format, and other related information that is not dependent upon a song selection currently being broadcast by the IBOC station. The lookup table would be constructed for a respective broadcast region that the receiver has been updated for. The frequency range or channel of the broadcast is used to index the lookup table to retrieve and display the station related information without having to decode the digital signal. A lookup table can be constructed or rebuilt automatically by the receiver or manually by a listener. An example of how the lookup table could be created or rebuilt is by using a scan function. Once the scan function is initiated, the receiver will scan through a broadcast band looking for digital broadcast stations transmitting a digital signal. When the receiver determines that a frequency range or channel is broadcasting a digital signal, the receiver will store the station related information for the digital broadcast station at a table entry in the lookup table. Each table entry in the lookup table will be associated with a respective frequency range or channel of a respective digital broadcast station. The lookup table could be used compare the identification codes of the lookup table with the identification codes of the received digital signal to verify that a digital broadcast station is present on the target frequency channel.
Since the lookup table is constructed for a specific geographical region, a listener cannot rely solely on the lookup table to verify the presence of a digital broadcast station for a target frequency channel because of the receiver being moveable in and out of various geographical locations. Additionally, when the listener performs a scan, seek, or tune operation to the target frequency channel of the digital broadcast station, the time to decode and produce the digital signal is longer than the time to decode and produce an analog signal containing information identifying the station as the digital broadcast station. It would be desirable to perform a fast tune operation for making a determination of whether the target frequency channel contains a digital data signal without having to decode the digital signal.